Conventionally, as an apparatus for performing various kinds of processing such as film-forming processing, etching processing and the like on a substrate, there is known a processing apparatus (a so-called cluster tool apparatus) which is constituted as shown in FIG. 1 by arranging a load-lock chamber B for the substrate and a plurality of processing chambers C in a manner to enclose a centrally positioned transfer chamber A having disposed therein a transfer robot 1. The processing apparatus is thus so arranged that a substrate S loaded into the load-lock chamber B can be transferred to the respective processing chambers C by means of the transfer robot 1. The transfer robot 1 is provided with a rotatable and telescopic robot arm 2. On a front end of the robot arm 2 there is mounted a robot hand 3 which supports the substrate S in a state of being placed on the robot hand.
In the course of subjecting the substrate S to various kinds of processing by means of the above-mentioned processing apparatus, there are cases where the substrate S is warped upward into a convex shape or is warped downward into a concave shape due to the difference in the direction of stresses and in the intensity of stresses depending on the kind and thickness of films that have been formed on the substrate. The warped substrate S is likely to become slidable because it does not come into surface contact with the robot hand. Then, if the speed of motion of the robot is accelerated to improve the throughput, the substrate S will give rise to a positional deviation on the robot hand 3.
Conventionally, as a robot hand in which this kind of disadvantages have been eliminated, there is known one, in patent document 1, in which a plurality of pads are attached to an upper surface respectively through spring members. According to this arrangement, even if the substrate gives rise to warping into convex or concave shape, each of the pads will be displaced to follow the warping, whereby the pads come into surface contact with the substrate. As a result, the frictional resistance between the pads and the substrate becomes equivalent to that when the substrate is flat, and the positional deviation of the substrate will thus be suppressed.    Patent Document 1: JP-A-2002-353291
However, in the above-mentioned arrangement described in the patent document 1, it becomes necessary to mount a large number of spring members on the robot hand, thereby bringing about an increase in cost. Further, the spring members are vibrated when the robot hand has come to a stop after movement, and if the substrate is handed over during the vibration, the substrate will be deviated in position. Therefore, it becomes necessary to wait for the vibration to stop before the substrate can be handed over. This will be an obstacle to an attempt in improving the throughput. In addition, if the robot hand is not held in a horizontal posture at the time of handing over, nonuniform load will be applied to the plurality of springs, resulting in a disadvantage in that the substrate will be deviated in a certain direction.